Since first looking at this post, I’ve been examining pictures of clinched nails on-line for anything resembling the find in question — and have found none. If anyone else finds one, please post.
In addition to the amount of effort it would’ve taken to make the swirl at the end, I find it interesting that the shaft of the find appears to be bent in the opposite direction of the swirl uniformly where the yellow line is. What would cause this bend if the find were a clinched nail?
Stepping back, I wonder if this was a slide-in hook of some sort? The head would slide into a slot and the eye of the swirl might have been used to run a string through.